Printing telegraph system controlled by vibrations of tuning forks



L. DEVAUX Nov. 25, 1947.

PRINTING TELEGRAPH SYSTEM CONTROLLED BY VIBRATIONS 0F TUNING FORKS Filed May 28, 1945 2 Sheets-Sheet 1 Nov. 25, 1947.

1.. DEVAUX PRINTING TELEGRAPH SYSTEM CONTROLLED BY VIBRATIONS OF TUNING FORKS Fild Ma 28, 1945 2 Sheets-Sheet 2 Jwm wNN 3 N NW r 'ummw rm n9 wQ NR M5 .3 Ii--- 5 L 9 J I g v INVENTOR. A UC/E/Y at max BY fie a, d 7

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Patented Nov. 25, 1947 PRINTING TELEGRAPH sYsrEM "eon- TROLIZED BYVIBRATIONS F TUNING "FORKS Lucien 'Devaux, Lyon, France, assi-gnor it'oz Intelf- 7 national Standard :Electric Corporation, New

York, N. Y.

Application Ma '28, 1943,--S eria'-l'No; l-8 8,861" In France June 30, 194].

8 Claims. 1

'I heesubjectof the invention is :a printing teles graph system having a simple mechanism, capable of being used in eflices having no electric power source and. suitable particularly Whenthe speed of transmission can, without objection, be made "relatively low'and 'can be subordinatedto ease of operation without needof g-reat "timeiin learning the operation thereof, conditions that arise particularly in small-rural oflices.

A general description ofthe invention is as follows. The transmitting device includes a keyboard similar to that of a typewriter, The depression of a key-produces first of all the passage of a a current, which simultaneously icbring into operation-two shafts, one located at the trans! mitte-r and one located atth e distant receiver, tneseshafts being driven byaclookwork. The tw'o shafts make a single turn at. substantially the same speed, this latter element being sy-n'chronized by means-of a tuning {forkin-each device. Durin a portion ofthis rotation the transmitter sends out pulses varying-in number, depending upon the key'depressed. At-the receiver, the P0 tatingshaft uses the received pulses to operate releasing electromagnets, which -in-turncause the rotation of a typewheel, this latter rotating through -a definite angle, depending upon the number of received pulses. The typewheel having thus been :brought into the desired position and the time interval allowed for the pulses having elapsed, the rotating shaft of the receiver causes the printing mechanism to operate .:in order to produce the printing of the character transmitted. Then it causes the paper tape -'-to advance While the-typewheelis being restoredto its starting position.

A feature of the present system residesin the combination-of the typewheel control-pulses so as to reduce to a minimum the total number of pulses for :each'character, Alternatingly positive and negative pulses aroused, and to each character is assigned a definite number-of such'positive and negative pulses.

Assuming that the number of difi erent characters to be transmitted is 49, that is, '7 times 7, the following combinations, for example, can be provided for:

Space-0 negative pulses,

Letter A-() negative pulses Letter B-0 negative pulses 0 positive pulses 1 positive pulse 2 positive pulses Letter tter '6 positive pulses '0 positive pulses F- 0 negative pulses G-l negative pulse Last mark-6 negative pulses 6 positive pulses The maximum total number of pulses -for 010- taining 4'9 combinations fi'S it'hus Seen to be 1-2.

L'Ithese lpul'ses, beingzpos'itive or negative, it is advantageous, in order to speed up'the operation, to alternateithe :pos'itive and the negative, pulses. In this mannerethetime'interval'that must'others wise necessarily: space two pulses of the .samesign is occupied by :the'emission oif aipulse=of opposite sign,fif needed, :so that 'the total time 'of 12.1p0sitive and negativeipulses cannot. exceed the duration of 6 pulses of the same sign spaced by '6 equal intervals. However, in practice, for :reasonsicoi-:mechanical.;.design, a :pulse .of one sign cannot be :followed instantly by a pulse; of opposite sign and :a small time interval :is necessary, which some-what lengthen's'the duration of; the 6 pulses.

Since the pulsesare alternated inpolaritv, the sending, )forex ample, of tthieletter Z, corresponding to 3 negativeipui e nd 5ipositive-pulses, will beefiected asiiollowszv The positioning of ,the .typewheel is effected step by step, but the steps corresponding to the negativeipulsesare of -ofasingle turn and those corresponding to the positive pulses are of A9 of a single turn. The pulses. 'for the letter Z will therefore cause the wheel't'o advance, as follows:

tate the construction of the devices andflmake themstutdy, f-to'use pulses of relative'ly long duration, forexample of-t'he \orader of 20 milliseconds,

which, with the small intenval 'elapsingbetweenthe pulses, gives about 02250 to-'0;300 secondi er the sending of:a--sing 1e='character. The printing, the return-to starting position of the typew heel and the advance of :thepaper: can all be effected in 0.200 to 0.300 second-sothat-the speed of transmission can reach 1.5 :to .2 characters per second, .afsp'eed that it is not practical to exceed, asthis-system is intended to be used by operators having, but little experience in the art.

A slow. rotational speed of the main shaft. of the tvpewheel is :an essential, requirement for the driving .oi the mechanism "by means :01 clockwork actuatedliby- 1 a :springv mequiring only feasible winding-up force and not too frequent replacement.

In the detailed description of the system that. follows, reference is made to the following drawings, where: 4 V

Fig. 1 shows one embodiment of a device according 'to this invention, for determining adjustment of the rotational speed of a. shaft by means of an escapement wheel. 7 I

Fig. 2 shows a portion of the pulse distributor of the transmitter sufiicient to illustrate the construction and operation thereof.

Fig. 3 shows one form of the mechanism of a keyboard key according to this invention.

Fig. 4 shows one form of the mechanism of the common pedal of one form of keyboard according to this invention.

Fig. 5' shows one form of themechanism of a typewheel aCCOrding to this invention,

Fig. 6 shows one form of the distributor of 'a receiver according to this invention.

Fig. 7 shows one form of the general layout of a complete telegraph station according to this invention.

As hasjust been explained, the transmitter and the receiver each use a shaft driven by clockwork, these two shafts rotating in synchronism. The arrangement used for obtaining the regular rotation of these shafts will therefore be first described.

In Fig. 1, the shaft whose movement must be regulated is shown at I. It is-arrangcd to be driven by clockwork including a spring 2 and a certain number of multiplier wheels, of which, in order to simplify the drawing, only two are shown at 3 and G. The movement of the shaft is arrested by an arm 5 resting against a stop 6 formed by the armature of an electromagnet I.

Shaft I is provided with an escapement wheel 8 the'teeth of which can be engaged by an escapement pawl 9 carried by the armature of another electromagnet III, each forward and return movement of the armature producing'an escapement, in two steps, equal to one tooth of wheel 8.

The movement of the armature of electromagnet If) is controlled by a tuning-fork I I. For this purpose, the circuit of electromagnet III is in series with the exciting coil I2 of the tuning-fork, which latter is in series with the contact I3, opened and closed by the movement of the prongs of the tuning-fork. While at rest, When arm 5 is bearing upon stop 6, the circuit of electromagnets I and I2 is broken by the opening of a contact formed by springs M, which latter are operated by an arm I mounted on shaft I.

In order to give the tuning-fork a starting pulse, a prism IB, attached to the end of an arm carried by shaft I, is placed between the prongs of tuning-fork I I, these prongs being bent so that in passing therethrough, when shaft I starts to rotate, prism IB will draw them apart slightly and then release them suddenly.

Toothed wheel 8 has a toothless portion II. In normal position, pawl 9 is facing the beginning of this portion I7, so that, when magnet 'I is energized and arm 5 is released, shaft I can turn through a small angle in the direction of the arrow before the first tooth of wheel 8 is engaged by pawl 9. This first movement is used for causing prism I6 .to force its way in between the prongs of the tuning-fork and to release them for starting the vibration. The vibration is maintained then, by magnet I2, which latter is suppliedby battery. IB'feeding electromagnet In via contact fork being regulated and constant, the time it I4,which latter was closed from the beginning of the rotation.

Each closing and each opening of contact I3 produced by the vibration of the tuning-fork causes a forward and return movement of pawl 9, and wheel 8 turns by the extent of one tooth, each time. The vibration period of the tuningtakes one tooth of wheel 8 to pass along is quite definite and, hence, the time required for a complete turn is constant. The rotation occurs by jerks, but damping springs may be provided between shaft I and wheel 8 in order to make the rotary movement regular to a certain extent and lessen the degree and force of the impact of the teeth of wheel 8 against the prongs of pawl 9.

All the tuning-forks of one and the same set of devices are adjusted to the same frequency, so that the speed of the shafts of two correspond ing devices is substantially equal; therefore, if the transmitter shaft is released at the same instant as the receiver shaft, the two shafts will constantly occupy the same angular positions at y a given instant. As will be explained later on, a

precaution is taken to compensate for any slight maladjustment in the speed of the shafts of two corresponding devices.

The system regulating the speed of the main shaft having been described above, no further reference need be made to it in the description that follows. Whenever shaft I is mentioned hereinafter, it will mean a shaft subjected to driving torque from a spring through clockwork and whose rotational speed is regulated by a tuningfork by substantially instantly bringing the tuning-fork into vibration as soon as the shaft, normally held by a pawl, is released.

Shaft I is common to the transmitter and to the receiver of one and the same telegraph station. It is normally engagedwith the receiver shaft, which hence istermed IR, so that this sta tion shall at all times be ready to receive a message. When this station is used to transmit a message, shaft I is separated from receiver shaft IR and is engaged with the transmitter shaft, which is termed IT. The engaging and disengaging operation -is performed automatically through the sending of a character, as will be hereinafter explained. v

The transmitter includes a keyboard for sending characters. mechanism whose function is first to send a current pulse of definite sign, which will be assumed to bepositive, so as to release shaft I simultaneously at each of two corresponding stations.

A single distributor, shown schematically in Fig. 2, serves to send out the current pulses in the order desired. It is composed of a series of spring contacts operated in sequence by an arm I9 mounted on shaft IT, a relay 20 cooperating with the distributor for the sending of the first pulse.

In the embodiment here shown, the springs consist of I3 groups numbered from 2| to 33, all

connected with battery 34 and with the ground,

as shown at 34'. When at rest, the springs of These keys put in operation a group 2| are depressed by arm [9. The negative pole of the battery is connected to the ground and the positive pole to the winding and to contact 35 of relay 26, the armature of which latter i connected to the circuit of receiver R and to the contact next to line conductor L.

As soon as a key is depressed, a contact 36 inserted in series in the circuit of relay 29 is closed and this relay, of the slow-acting type, operates after a short time. The positive pole of battery 34 is connected to receiver R and to line L via contact 35. The positive current of the battery travels through the two polarized relays of the corresponding stations, a line-resistance compensating resistor being inserted in the circuit of the relay of the transmitting station. The result thereof is that the relays of the two stations in communicaion operate simultaneously and close the circuit of the magnets releasing shafts I of both stations. The two shafts therefore start together and their movement is continued synchronously, as has been explained.

Immediately after the starting operation, line conductor L is transferred from the receiver to the transmitter through the opening of contact 31. The passage of arm [9 under spring groups 22 to 35 produces successively the grounding of the positive and of the negative pole of battery 34, this permutation being repeated six times, the other pole being connected each time to wires 38 to 49. The even wires correspond to the negative pulses and the odd wires to the positive pulses. The keyboard keys serve to connect wires 38 to 49, in suitable fashion, to line L, for the sending thereover of the number of pulses, of each sign, corresponding to the code symbol for the particular character to be transmitted.

A negative pulse can be sent by connecting wire 38' to the line, two pulses with the use of wire 46, three with the use of wire 42, etc., and finally six with the use of wire 48. one negative pulse, wire 4| sends two, etc., and finally wire 49 sends six. The keyboard keys must therefore be arranged so as to close two contacts that will connect the distributor to the line at two suitable points, it being understood that, when the code of the letter comprises a zero, the pulse springs, regardless of whether positive or negative pulses are involved, are not connected at all to the line.

It has been above stated that relay 29 was slow acting. This time lag constitutes a precaution against the effect of a slight default in synchronism between the corresponding stations. It is, in fact, necessary that at the beginning of each signal the shafts of both stations be exactly at their null positions. If, owing to a slight maladjustment, the receiver should be lagging with respect to the transmitter, it could not catch up with it in case of signals being transmitted, without stopping, and the synchronism would thereby be destroyed. The time lag provided by relay offsets such possible defect, by causing the transmitter to make a stop for a short period, thus giving the receiver shaft time to complete its rotation, regardless of the direction of the trans- 1111851011.

The pulse distributor having been described, the mechanism of the transmitter keys will now be explained, one of these keys being shown in Fig. 3.

This key includes a lever 50, provided with a button 5! bearing the designation of the character to be transmitted thereby. The lever pivots on a rod 52 and is pulled upwards by a spring 53.

Likewise, wire 39 sends Lever 5 Uicarries a pivoting hook 54, which a spring? 55 keeps engaged with the end of a lever 56. This latter pivots on a rod- 51 and a spring 58 keeps it inits normal position. Lever 56 carries a tongue: 59, which pivots on a pin 69 and which, when at rest, is maintained between a stationary bar BI and a member 62 oscillating around a stationary rod 63'. An interponent 64 attached to member 62 serves to operate a spring 65 to cause it to close the contacts of springs 66 and 61.

When a key 5| is depressed, hook 54 causes lever 56. to rock and. tongue 59 is introduced between an oscillating bar 68 and member 62. Bar 68 is carried by arms 69 pivoting around rod 16, one of which arms carries a roller II that can be driven by the end of an arm I2 mounted on transmitter shaft IT.

The depressing of a key further entails the depressing of common pedal 13, carried by arms 14 pivoting on red I5. A spring 16 tends to maintain this pedal in its raised position. It is pedal 13 that closes the contact 36 (Fig. 2) causing the operation of relay 26 and the sending of the first starting pulse. In addition, by means of driving-- gear not shown in the drawing, pedal I3 serves to disengage receiver shaft IR, normally engaged with the clockwork shaft I (Fig. 1), and to engage this latter shaft with the transmitter shaft IT. Consequently, as soon as pedal I3 is depressed through the operation of any key, the starting pulse is sent out, and shaft IT starts to turn in the direction of the arrow. I

Arm 12 drives roller II and bar 68 drives tongue 59, which latter, in moving, drives member 62. Interponent 64 then closes the contacts between spring 65 and the two springs 66 and 61. Member 62 is locked immediately in position by catch 11, which, under the urging of spring 78, engages the notch of member 62.

Contact spring 65 is connected to the line wire. Contact spring 66 is connected to one of the even numbered contact springs 38 to 48 of the distributor so as to send out the desired number of negative pulses. Likewise, contact spring 61 is connected to one of the odd numbered contact springs 39 to 49 so as to send out the negative pulses.

As soon as catch I1 engages the notch of mem= ber 62, an arm 19 drives a roller carried by one of arms 8|, pivoting on a rod 82 and carrying a bar 83; this latter drives an enlarged extension of hook 54, disengaging the end of lever 56, which, under the urging of spring 58, returns to its normal position by disengaging tongue 59. Bar 83 normally is drawn out of the path of lever 56 by spring 84, but member 62 remains locked for the duration of the transmission of pulses, caused by the rotation of shaft IT which drives the distributor cam (Fig. 2).

Immediately after the transmission of the pulses, a third arm 85 acts upon roller 86, carried by lever 81, which forms part of catch 11, This latter releases member 62, which returns to its normal position, thus opening the contacts of springs 66 and 61, the function of which is now completed.

Fig. 4 serves to explain the operation of pedal 13. One of the arms I4 of this pedal carries a hook 88, similar to hook 54, pivoting on a rod 89 and provided with a spring 96 that tends to keep it engaged with the end of a bell-crank 9|, pivoting on the same rod 51 as lever 56. Lever 9| is pulled by a spring 92 and it is provided with a pin 93 lodged in a hole at the end of a conmeeting-rod 94, which latter is forked at its other end. ,The fork is engaged by astud95 attached. to a catch memberilt.pivoting-ontrunnions 91.,

Bar 96, common to all the keys, serves t jengage draws stud 95 to the bottom .of the forks Bell-crank 9| serves to' close the, operation;

controlling contact 36 inserted in series with the circuit of relay 28 (Fig. ,2), and in addition it controls, via a connectionv not shown in the drawing, the disengaging of the receiver shaft and the engaging of the transmitter shaft. 7

When a key is depressed, pedal-13 is operated and, under the action of latch-88, bell-crank 9| is rocked, driving connecting-rod 94. Catch bar 96,-,drawn by spring 96, engages latch 98, which latter action prevents the depressed key from again rising. But as soon asshaft IT has commenced its movement and member 62 is locked by catch TI (Fig. 3) ,bar 83 pushes the enlarged portion of latch 88 and releases lever 9|, which then returns to normal, Contact 36 (Fig, l), which is nolongerin use, is opened, catch bar 96 is pushed back, and the depressedkey can then rise. The release of lever 8| does not entailthe disengagement of shaft IT, because the clutch mechanismis of the type of those used in printing telegraph apparatus and remains engaged untilthe shaft has made a complete turn. Thus the movement of the transmitter shaft continues, regardless of the position of pedal'IS.

If the operator keeps the key down, the trans mitter will stop after having made onecomplete turn, for the reason that, lever Ill being at rest, the disengagement of the transmitter shaft occurs after the completion of such turn. I

Normally, the operator should allow the key to rise. He then can without waiting for the shaft to make the turncorresponding to the sending of a first transmitted character, prepare the sending of the next character by depressing a second key., The rising or restoration of thefirstkey, and of the pedal, relocks levers 56 and SI, and the depressing either of the samekeyor of another key produces the closing of contact 36 and the latching of the depressed key. Shaft IT is not disengaged at v the end of the first turn. An interval for the stoppage is provided by the time keyfr om'bein g depressed when some other key isalready locked. l

U The transmitter pulse-sending device il i aving been described above, there remains tobe ex plairied the use of the pulses 'by the receiver for the positioning of the typewheel and the operating functions of the receiver itself. n

The main part of the receiver is the typewheel, with its control mechanism. The typewheelis a light weight wheel with raised characters around its periphery It is inked by a small felt;pad impregnated with preferably greasy ink, which pad bears lightly at one point. Since the type wheel makes one complete turn for each character transmitted, all the characters pass'constantly under the pad. I j

The movement of the wheel is controlled by epicycloidal gearing so that the negative pulses cause it to rotate by sevenths of a-turn jand the. positive pulses by sevenths of a seventh, i. e., by

forty-ninths of a turn. .Therefore, when the letter P, the code of which is 23, isreceived the first negative pulse causes the wheeltorotateby one seventh of a' turnythenthe next positive pulse causes it to rotate by oneiorty-ninth; the

second negative pulse causes it to rotate by a second seventh and the next two positive pulses cause it to rotate by two forty-ninths of a turn. The wheel therefore rotates through a totalangle of 7+% i. e., /4 of a turn, and places the letter P in front of the printing bail.

Afterthe printing, the wheel continues its movement, so as to return to its initial position, by means of; pulses produced locally in the ,receiver..-

The typewheel control mechanism is shown, by way of example, in Fig. 5. The typewheel I00, upon which bears inking-roller I6I, is mounted onshaft IR, which is subjected to the action of main spring I03 through a differential associated with one of the clockwork wheels. For example, spring I03 drives wheel I64, which meshes with pinion I65, mounted on shaft I66. This shaft carries arm I67, on which pivots a satellite pinion I68 that transmits the torque of spring I03 to two wheels, I69 and III Wheel I69 is integral with a wheel I I I, this latter meshing with pinion H2, which forms part of the clockwork driving main shaft I. The other wheel (I It) is integrally connected to a wheelII3, this latterwheel meshing with a pinion H6 mounted on shaft IR, which thus receives the torque of the driving spring.

Shaft I 62 carries an arm H5 constituting the supporting bearing of a satellite pinion H8, this latter meshing with two toothed wheels, I II and H8. Wheel II? is associated with a wheel ll9 meshing with a wheel I28 mounted on the same shaft I2I as a seven-tooth escapement wheel I22 which is engaged by a pawl I23, mounted on the armature of an electromagnet I24. The torque of shaft IR, is therefore transmitted to wheel I22, and each forward and return movement of the armature of electromagnet I24 allows one tooth of the wheel to escape. II9 has 30 teeth'and wheel I25} has 60, so that the escapement of each tooth of wheel I 22 causes wheel I2fl to rotate by one seventh of a turn, wheel H9 rotates by two sevenths and, through gearing I-I I--I I6, shaft I R rotates by one seventh of a turn, driving the typewheel. Similarly wheel I teeth, so that each tooth of wheel I28 causes wheel I25 to rotate by two sevenths of a seventh of a turn, 1. e., two forty-ninths of a turn, and.

shaft IR, rotates by on forty-ninth of a turn. The typewheel is therefore positioned by the movement of the armatures of electromagnets I24 and I30, electromagnet I243 making it advance by steps of one seventh of a turn and electromagnet I39 by steps of one forty-ninth of a turn.

The movement of the electromagnets is obtained by connecting them to the respective negative and positive contacts of a polarized relay receiving the line current, as will be hereinafter explained.

After the printing has been accomplished, the typewheel is restored to its starting position by completing its rotation, this movement being controlled electrically.

I he distributor, which will hereinafter be referred to in detail, closes the local circuit of electromagnets I24 and I36 viaa contact I3I in series with contacts operatedby the escapement wheels.

Wheel The circuit of electromagnet I24 includes a pair of springs I32, the contact of which is'closedat with springs I32, a second pair of springs I34,

the contact of which is closed as soon as typewheel I 0.0, and hence shaft IR, has rotated by one seventh of a turn. This latter contact is opened by insulating cam I35, when wheel I has to make but /49 .of a turn, .or less, before reaching its normal or null position.

The circuit of electromagnet I30 includes only one pair of springs I36, th contacts of which can be closed by six pins I 3], carried by six of the teeth of wheel I28. The seventh tooth, which carries no pin, arrives in front of springs I36 when wheel I00 is in normal position, or' when its position does not differ from the normal position but by an exact number of sevenths of a turn.

When contact I3I is closed by the distributor, after the printing, the current from battery I33 travels through one or the other of electromagnets I 24 and I30, or both, depending upon the position of wheel I 00. Immediately the electromagnets attract their respective armatures, which causes wheels I22 and I28 to turn by half a tooth, thus opening the contacts of springs I32 or I36, respectively. The armatures fall back, the whee advancing again by half a tooth, and closing the contacts. This operation is repeated for electromagnet I 24 until the contacts of springs I 34 are opened, which indicates that wheel I00 has less than one seventh of a turn to make before reaching its normal position. For electromagnet I30, its operation stops when the pinless tooth of wheel I28 arrives in front of springs I36, which means that wheel I00 has rotated by an exact number of sevenths of a turn. The typewheel therefore returns to its normal starting position.

The receiver distributor is shown in Fig. 6. Its function is to establish the circuits intended for the reception of the starting signal, the control of the advance of the typewheel according tothe received pulses, and the return of this wheel to its normal position. 7

Receiver shaft IR, normally engaged with main clock-work-driven shaft I, carries an arm I39 acting as a cam. At the beginning, when the receiver is idling and awaiting the receipt of a message, arm I39 closes the contact I40, thus connecting the positive contact of polarized line relay MI to starting electromagnet I (Fig. 1). When a positive pulse is received, electromagnet I is energized and shaft I and, hence, shaft IR are both brought into operation.

Immediately afterwards, the positive contact of line relay I II is removed from starting electromagnet I and is connected by springs I42, actuated by cam I43, to electromagnet I30 (Fig. which series of steps serves to advance the typewheel by forty-ninths of a turn. The width of cam I43 is such that the duration of the .closing of the contact of springs M2 corresponds with the transmission time of the pulses determined by the transmitter operation. Since, on the other hand, the negative contact of relay I4! is connected permanently to the electromagnet I24, causing the advance by sevenths of a turn, the result is that at the end of the pulses causing the movement of the armature of relay I4I, typewheel I00 has arrived at the desired position.

At this moment, a cam I44, carried by shaft IR, mechanically actuates the printing bail (not shown) carried by lever I45. Immediately afterwards, another cam I48 closes the contact. of the springs I3-I inserted in the local circuit of electromagnets [2.4 and I30, for causing the return to normal of the typewheel (Fig. 5) Contact I3I remains closed until the end of a single rotation of shaft IR, so as to give the typewheel the total time required for it to make a complete turn.

During the passage of .cam I I under springs .I3I, another cam causes the paper tape to advance.

At theend of one complete turn of shaft IR, the positive contact of relay I40. is connected again ,to starting magnet I, so as to await the next signal.

Fig. '7, showing an example .of a general layout .of a complete station, serves to show the connections between the various .elements that have been above described, separately, the same reference numbers having been affixed to the various members. In .order to avoid complicating the drawing to the point of making it illegible, the springs of the transmitter distributor have not been shown in ,detail, and the cams and other members the function of which is merely mechanical are not shown. The mechanism used to disengage receiver shaft IR and to.-engage transmitter shaft ITjwhen a key is depressed. is represented wholly schematically by slider I IZI, operated by a bell-crank I438, which letter is itself controlled by connecting-rod 9, 3. The slider carries two forks I49 and. I 50, respectively acting so as .to cause members I5I and I52 to slide on shafts. IR and ,IT and so as to cause them to engage in the respective holes of discs I53 and I54 or disengage them therefrom. 7

Line wire L normally is connected to polarized relay I II via contact 31, and consequently the station is alwaysready for reception. 7

When the device is used for transmission, the depressing of a key engages shaft IT, disengages shaft IR an'd,by closing contact 36, causes the operation of slow-acting relay 20, which latter sends'out the starting pulse by connecting the positive pole of battery 34 both to line wire L and to relayI II. Resistor I55 is inserted in series with relay MI by the opening of contact I56, to compensate for the line resistance and to cause the two relays I I I of'the transmitter and of the receiver .to operate substantially simultaneously.

As soon as the transmitter shaft has commenced to rotate, contact 37 is opened and the negative and positive pulse's'constitutingthe code of the signal to be transmitted are sent by the distributor via the contact springs 65, IES'and 0'! of the key whichhas been depressed.

It is possible to receive locally the transmitted message by eliminating the action of fork I50, so that the receiver remains engaged during the transmission, and by also keeping the line wire connected to relay MI "by 'means of-key I50.

In case it is deemed desirable to use only pulses of the same sign, instead of alternating positive and negative .pulses, the following modification affords the possibility of so doing. The transmitter distributor sends out two separate series of pulses of the same sign. The first series corresponds to the negative pulses from 0 to 6 and the second series to the positive pulses, also from 0 to 6. At the receiver, polarized relay IAI is replaced by a simple relay and the receiver distributor first connects the contact of this relay to electromagnet I24 during the time reserved for the pulses of the first series, then to electromagnet I30 during the time reserved for the obtained by changing the sign, it is necessary to reduce the length of each one of them, which entails a much more precise and fine construction of the apparatus.

The system that has just been described is intended for wired circuits, but it can evidently be adapted to radio links by replacing the positive and negative pulses by the modulation of the carrier wave with two frequencies and by separating these latter frequencies at the receiving end, by means of filters or resonant circuits.

While certain embodiments of this invention have been shown and described, these are purely illustrative and the invention is limited only by the scope of the hereunto appended claims.

. What is claimed is:

1. In a printing telegraph system, a receiving type-wheel, an intermittently operated driving escapement wheel, a tuning fork controlling the rotation of said escapement wheel and means for setting said tuning fork into vibration when said escapement wheel starts to rotate, said last means including a prism mounted so as to rotate in synchronism with said escapement wheel and positioned so as, upon rotation, to pass through the arms of said tuning fork and engage said arms so as to set said fork into vibration.

2. A system according to claim 1, also including at the transmitter anintermittently rotating impulse sending arm and means for producing and transmitting a starting current pulse to both transmitter and receiver rotating drives, whereby said rotating arm and said escapement wheel are synchronously set into motion.

3. A system according to claim 1, also including at the transmitter an intermittently rotating impulse sending arm and means for producing and transmitting a starting current pulse to both transmitter and receiver rotating drives, whereby said rotating arm and said escapement wheel are synchronously set into motion, and also including at said transmitter a slow-acting relay determining the start of rotation of said arm, and means for sending said starting pulse through said relay to compensate for any difference in time of operation between said transmitter and said receiver. 4. System according to claim 1, also including at the receiver a distributor actuated synchronously with the rotation of said escapement wheel and acting to cause the starting, the positioning of the typewheel and the return thereof to the starting point.

5. System according to claim 1, also including at the receiver adistributor actuated synchronously with the rotation of said escapement wheel and acting to cause the starting, the positioning of the typewheel and the return thereof to the starting point, also including means for controlling the rotation of the typewheel including the advance thereof through large and small angles,

" said means including two escapement wheels,

electromagnets controlling said escapement wheels, epicycloidal gearing and a differential connecting said escapement wheels and said typewheel, the operation of said electromagnets cori responding with negative and positive pulses, re-

wheel and the typewheel, so as to drive both said wheels from said single source.

'7. A system according to claim 1, also including at the transmitter an intermittently rotating arm and means for producing and transmitting a starting current pulse to both transmitter and receiver elements, whereby said rotating arm and said escapement wheel are synchronously set into motion and likewise including at both stations of said system means for controlling the transmitter and receiver rotating shafts, the transmitter shaft normally being engaged and means whereby the depressing of a key of the keyboard produces at the receiver, simultaneously,'the disengagement of said transmitter shaft and the engagementof said receiver shaft.

-8. A system according to claim 1, also including 1 at the. receiver a shaft mounting-said escapement wheel, at the transmitter an intermittently rotating impulse sending arm, a second shaft mounting said arm, and means for producing and transmitting a starting current pulse to both transmitter and receiver rotating drives, whereby said rotating arm and said escapement wheel are .synchronously set intomotion and likewise ineluding at both stations of 'said system means for controlling the coupling ofsaid transmitter and receiver rotating shaft s, means'normally engaging thetransmitter shaft with the receiver shaft and means Whereby'the depressing of a key of the keyboard produces at the receiver, simultaneously, the disengagement of said transmitter shaft and the retention of the engagement of said receiver shaft, also including additional means at the transmitter to prevent the operation of the means for normally disengaging said receiver shaft at the transmittenwhereby the transmitted ,file of this patent:

UNITED STATES PATENTS Number Name Date 7 2,128,242 Graham et a1. Aug. 30, 1938 2,082,575 Harris0n' June 1,1937 2,247,162 Beccio June 24, 1941 1,000,078 Cummings et a1. Aug. 8, 1911 

